Crop description. Pongamiapinnata (L.) Pierre, P. glabra Vent., Cytisus pinnatus L., Derris indica (Lam.) Bennett, and Galedupa indica Lam.— commonly known as karanja, pongam, coqueluche, Vesi Ne Wai, vesivesi, hongay, and honge—belong to the Leguminaceae family and are widely distributed in tropical Asia (see Fig. 4.7). The tree is drought-resistant, tolerant to salinity, and is commonly found in East Indies, Philippines, and India. The karanja tree grows to a height of about 1 m and bears pods that contain one or two kernels. The kernel oil content varies from 27% to 39% and contains toxic flavonoids, including 1.25% karanjin and 0.85% pongamol [86-88]. The fatty acid composition consists of oleic acid (44.5-71.3%), linoleic acid (10.8-18.3%), palmitic acid (3.7-7.9%), stearic acid (2.4-8.9%), and lignoceric acid (1.1-3.5%) [86, 89].

Main uses. The oil is used mainly in agriculture, pharmacy (particularly in the treatment of skin diseases), and the manufacture of soaps. It has insecticidal, antiseptic, antiparasitic, and cleansing properties, like neem oil [86-88]. The cake after oil extraction may be used as manure.

Figure 4.7 Pongamiapinnata (L.) Pierre. (Photo courtesy of the Food and Agricultural Organization of the United Nations[www. fao. org].)

All parts of the plant have also been analyzed for its reported medical importance. Several scientists have investigated and guaranteed karanja oil as a potential source of biodiesel [78]. Most researchers have conducted the transesterification of P. pinnata oil by using methanol and potassium hydroxide catalysts [90-92]. Meher et al. [90] found that using a methanol-oil molar ratio of 12:1 produced maximum yield of biodiesel (97%), while Vivek and Gupta [91] stated the optimum ratio was 8-10:1. In both cases, the optimal temperature was around 65°C, with a reaction time of 180 min [90] and 30-40 min [91]. Vivek and Gupta used 1.5% w/w of catalyst (KOH), while Meher et al. used 2% w/w solid basic Li/CaO catalyst [93]. Due to the high FFA (free fatty acid) content, some researchers have proposed esterification with H2SO4 prior to trans­esterification with NaOH [94, 95]. In all cases, karanja oil has shown a feasibility to be used as a raw material to produce biodiesel, saving large quantities of edible vegetable oils. Diesel engine performance tests were carried out with karanja methyl ester (KME) and its blend with diesel fuel from 20% to 80% by volume [92]. Results have revealed a reduction in exhaust emissions together with an increase in torque, brake power, thermal efficiency, and reduction in brake-specific fuel consumption, while using the blends of karanja-esterified oil (20-40%), compared to straight diesel fuel.